It isn't 100 HP. it is ~250 HP with all the changes. He's making that engine go as hard as it possibly can.

http://experimenter.epubxp.com/i/434207-dec-2014/23


Most of it comes from the extra power.

Even then, he only got to 260 HP is a very light (900 lbs), very small, very low frontal area airplane.

Now think about 230 HP going 285 KTAS in a much larger, heavier airplane, while delivering pressurization as well.

Ain't going to happen.

Mike C.

It isn't 100 HP. it is ~250 HP with all the changes. He's making that engine go as hard as it possibly can.

http://experimenter.epubxp.com/i/434207-dec-2014/23


Most of it comes from the extra power.

Even then, he only got to 260 HP is a very light (900 lbs), very small, very low frontal area airplane.

Now think about 230 HP going 285 KTAS in a much larger, heavier airplane, while delivering pressurization as well.

Ain't going to happen.

Mike C.

So it is.

In any case, the Determinator gave us a reference for HP and speed which indicates the infeasibility of the Raptor numbers.

Mike C.

You can't make an equation that calculates a ratio of speed to horsepower without considering many other variables, notably drag.

The main claim that the Raptor team makes is low drag and an efficient airframe design that wasn't possible before the computer design process.

Cool. Explain how.

Sure you can.

Drag and HP are linearly related. 15% less drag and 15% more HP do the same thing to the first order.

Speed and HP/drag are cubic related. 15% more HP or 15% less drag is 5% speed change. Double the HP or half the drag, only changes speed 26%.

The net result is that it takes ENORMOUS drag or HP changes to create really significant speed changes. The Raptor "designers" did not find some magic elixir that cuts the drag in half. Cutting it by 15% is miraculous enough.


The Determinator was tweaked to be low drag as well, the article I referenced spent considerable time going over the many details. Given it is a racer, not certified, it is very doubtful the Raptor folks can be as good for something that can be certified.

Mike C.

I figured you needed something other than check valves.

I would be surprised if you can make a practical flow fuse for coolant on the supply line. It works for hydraulics because they are high pressure and relatively low flow, coolant is low pressure and high flow. The fuse senses the big change in pressure and seals off. In low pressure coolant, a medium leak would not change the flow or pressure that much, and pump out the coolant supply in a minute or two.

You could make two separate coolant systems, two pumps, two isolated channels in the engine, but the engine is an automotive derivative so it lacks that in the design.

Even if you can isolate one wing, you are down to half your system.

This is not a new idea, the Mosquito in WWII had inboard leading edge radiators, among others. it has good properties aerodynamically, but it generally isn't enough to serve as anti ice for piston aircraft, just not enough waste heat, particularly for a high efficiency diesel.

Mike C.

So I am curious, how many folks here would be willing to get into a single engine plane powered by a car engine?

I mean, big companies like CMI etc. have been working for years (quite unsuccessfully) to build an aviation diesel, and this guy is just going to stick an Audi engine in it and fly away?

It would be a hoot to see Rutan read the numbers for the Raptor and see how much he laughs.

Burt knows the numbers. Give him the weight, frontal area, wing area, Cd, HP, and I bet he can estimate the cruise speed to within 10 knots.

The Raptor is not exploring some new frontier, it is decidedly in territory that has been well understood for decades.

Mike C.

Let's see. It is 15% more efficient than a Cirrus so it goes 50% faster, burning half the fuel, carrying half more weight and it travels twice as far...but it is made out of space age carbon fiber with a state of the art Diesel engine with all the latest and greatest glass cockpit for 1/4 of the price of the Cirrus but we want to get it down to 1/5 of the price. Very doable.

There was a really great little jet that did this a while ago but it's model was one third as unrealistic as this one. How did that work out? Probably a lot better than the Moller car. But wait. We could build a new modern flying car and with a few improvements we could surely put one of those in every garage. How is that one coming. If it is not ready yet maybe we should make that one a VTOL 4 seat car, cause the 2 seat horizontal take off one can only barely fly. I am sure that a 4 seat VTOL one will be much better.

Why spend $3K on a deposit, when I can count on Santa Claus to get one down the chimney way before they get this one done.

I don't see where they are asking for investment money.

I see where they are asking for refundable deposits and that falls under the CFTC. They are having that money deposited in escrow.com. They don't touch the money or get any use of it.

Very different situation then the way Eclipse handled customer deposits.

To me it looks like a local EAA chapter experimental project in watching the build.

Don't tell diamond aircraft

I'd fly a Corvair-powered Pietenpol in a heartbeat. Maybe not the Model A, though.

I figured you needed something other than check valves.

I would be surprised if you can make a practical flow fuse for coolant on the supply line. It works for hydraulics because they are high pressure and relatively low flow, coolant is low pressure and high flow. The fuse senses the big change in pressure and seals off. In low pressure coolant, a medium leak would not change the flow or pressure that much, and pump out the coolant supply in a minute or two.

You could make two separate coolant systems, two pumps, two isolated channels in the engine, but the engine is an automotive derivative so it lacks that in the design.

Even if you can isolate one wing, you are down to half your system.

This is not a new idea, the Mosquito in WWII had inboard leading edge radiators, among others. it has good properties aerodynamically, but it generally isn't enough to serve as anti ice for piston aircraft, just not enough waste heat, particularly for a high efficiency diesel.

Mike C.

Just sounds like all this plumping and piping and heat exchangers add more complexity and weight when they are trying to create an efficient, low cost, easy to build and maintain aircraft.

These type of things are why new type designs from the Starship to the Eclipse 500 don't meet their early design objectives. Always seem to start one way and end up the other.